GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 based on the development of the project ITHACA (2019). In particular this project was realized to research and describe the capable faults, defined as faults that potentially can create permanent coseismic deformation on the surface. According to this catalogue the area does not present active and capable faults. Moreover, by analyzing the DISS (Database of Individual Seismogenic Sources) catalog, published by INGV (2021), the territory of the Municipality of San Vito Lo Capo does not result affected by any seismogenic element and the presence of active and capable faults is not reported. Nevertheless, a fault located in the western part of San Vito Lo Capo and indicated in pre-existing geological cartography, results poorly investigated and for this reason it was not possible to clearly identify deformation or morphostructural evidence of recent movements. Therefore, on the basis of the available data it was not possible to reconstruct the extent of the fault displacement and the age of the movement. Data collection As required by the SM guidelines for the study of first level, a collection of pre-existing geognostic and geophysical data has been used. These was appropriately selected basing on the reliability of the results that is linked to the methodology data acquisition and processing. As regards geognostic surveys, ten pre-existing continuous core drilling were used to improve the information about the subsoil and to calibrate the depth of the seismic bedrock since five of them reach the geological substrate. Geophysical data analyzed included Seismic Refraction surveys (SR), Vertical Electrical Soundings (VES), Electrical Resistivity Tomography (ERT) and noise seismic data elaborated using the Horizontal to Vertical Spectral Ratio (HVSR) method. 52 SR investigations were carried out during public or private professional studies for the determination of the compression waves velocity useful to define the bedrock depth. These surveys were realized both in San Vito Lo Capo, Macari and Castelluzzo. The depth of investigation of almost all surveys did not exceed ten meters due to the detection of the seismic bedrock within this depth in all investigated areas. In a large area upstream of the village of Castelluzzo seven VES were performed, whose interpretation allowed to reconstruct the local stratigraphy up to depths of about 100 m below ground level. The results of these surveys cannot be fully validated because due to the lack of fundamental information concerning the acquisition parameters and the resistivity curves obtained from the measured values. In addition, other information was provided by five ERT carried out in the town of San Vito Lo Capo.